import { HttpQueryError } from "./types";
export declare function hasHeader(headers: HeadersInit | undefined, name: string): boolean;
export declare function isJsonSerializable(value: unknown): boolean;
export declare function serializeBody(body: unknown): BodyInit | undefined;
export declare function parseJsonSafe<T>(text: string): T;
export declare function toHttpQueryError(err: unknown, defaultMessage?: string): HttpQueryError;
export declare function sleep(ms: number): Promise<void>;